Add more instructions to install pyjs-code-runner

[jtpio]

Expand the README to mention how to install pyjs-code-runner locally:

• add dev install
• add example log

[jtpio]

cc @DerThorsten for review.

If you would like to I would be happy to help get a release out on PyPI so the install process is a bit simpler.

[DerThorsten]

If you would like to I would be happy to help get a release out on PyPI so the install process is a bit simpl

@jtpio any help is appreciated !

[jtpio]

Cool. Then maybe we can get the other PRs in as well before the first release.

It would also make sense to use the Jupyter Releaser which should be simple to set up. But I'll need Admin access to the repo for this since it's required by the releaser to be able to push the tags and release commit.